[Linux-cluster] RHEL Upgrade running RHCS/GFS

I will be upgrading from RHEL4 to RHEL5, on a two-node cluster.
I am using blade_center fencing, which is my biggest concern.

I want to put all apps/dbs on node-2, then upgrade node-1.
After node-1 is good, I want to attach it to the cluster, and fail-over all apps/dbs from node-2 to node-1.
Then I will upgrade node-2, attach it to the cluster and be done.

My biggest concern is with the fencing mechanism, i have seen it go buggy.
What could I do to control fencing, while I upgrade the other servers? I need the apps/dbs up and running while I upgrade.